Vision systems that perform measurement, inspection, alignment of objects, and/or decoding of symbology, such as one-dimensional and two-dimensional barcodes, are used in a wide range of applications and industries. These systems are based around the use of an image sensor, which acquires images of an object, and processes these acquired images using an on-board or interconnected vision system processor. The image is typically captured as an array of image pixels each having various colors and/or intensities.
A common use for such imaging systems is to track and sort objects moving along a conveyor in manufacturing and logistics operations. Typically, such imaging systems capture all sides of an object being tracked, which results in capture of six sides of a cuboidal object in many cases. In such systems, it is necessary to capture the bottom of the object, which is the side of the object that is in contact with the conveyor.
In some instances, a line-scan camera can be employed to address object movement and a wide field of view. However, such solutions are not applicable for certain object geometries and line arrangements. In addition, while line scan image sensors tend to be less costly than conventional format area scan sensors, the overall system costs of using line scan image sensors may be significantly higher, due to increased computation and processing requirements. For example, line scan image sensors require a complete image to be reconstructed in software line by line. Further, alignment of object motion and image acquisition timing is critical.
Area scan image sensors image a defined area quickly and allow easier setup and alignment and greater flexibility than line scan sensors. However, even with area scan image sensors, due to factors such as the size of the object, the resolution of the imager, the geometry of the conveyor, etc., only partial views of the object may be captured. Accordingly, some processing to reconstruct a complete image may be needed.
Another consideration is which sides of the object are to be imaged, as the system configuration may differ depending on whether the bottom side, top side, or other sides of an object are to be imaged. For example, in some applications, several or all sides of an object are to be imaged, including the bottom side. In other applications, imaging of only one side is required. For example, the bottom side may be imaged instead of the top side so as to avoid complications relating to imaging objects with different heights, which may have different distances from the camera.
In some applications, one camera or more cameras may be used to image each side of an object, while in other applications, two or more cameras may be used to image one side of an object. In applications in which one side of an object is to be imaged, a single standard-resolution camera may not provide adequate resolution, and an adequate coverage area and two or more cameras may be used to image that side of the object.